import java.io.*;

import java.sql.*;

import java.text.*;



/** object wrapper for the database.

 * @author anders

 *

 * basically just isolates all the database specific code so we could,

 * if we wanted to, change the entire database backend simply by

 * changing this one class.

 */



public class DBWrapper {

    

    Connection db = null;	// The connection to the database

    Statement  st = null;	// Our statement to run queries with

    //    PrintWriter out = res.getWriter();  

	

    String url = "jdbc:postgresql:network"; 

    String usr = "anders";

    String pwd = "foo";



    /** default constructor.

     * @author anders

     */

    public DBWrapper(){

	super();

    }



    /** establishes connection to database.

     * @author anders

     * @return true if connection established, false if problems

     */

    public boolean connect(){

	try {

	    // Load the driver

	    Class.forName("org.postgresql.Driver");

	    

	    // Connect to database

	    db = DriverManager.getConnection(url, usr, pwd);

	    return true;

	} 

	catch(ClassNotFoundException e) {

	    System.out.println("Couldn't load database driver: " + e.getMessage());

	    return false;

	}

	catch(SQLException e) {

	    System.out.println("SQLException caught: " + e.getMessage());

	    return false;

	}

		

    }



    /** gets an xml formatted list of edge data.

     * @author anders

     * @return xml formatted list of edge data

     */

    public String getEdgeList(){

	String temp = "";

	try {

	    st = db.createStatement();



	    ResultSet rs = st.executeQuery("select source,dest,weight,class from example");



	    while(rs.next()) {

		String source = "<source>" + rs.getString("source") + "</source>";

		String dest   = "<dest>" + rs.getString("dest") + "</dest>";

		String weight = rs.getString("weight");

		weight = (weight == null)

		    ? "<weight>50</weight>" : "<weight>" + weight + "</weight>";

		String e_class = rs.getString("class");

		e_class = (e_class == null)

		    ? "<class>default</class>" : "<class>" + e_class + "</class>";

		temp += "<edge>" + source + dest + weight + e_class + "</edge>\t";

	    }

	}

    

	catch(SQLException e) {

	    return "SQLException caught: " + e.getMessage();

	}

	

	return "<edge-list>" + temp + "</edge-list>";

    }



    /** gets a list of the node data.

     * @author anders

     * @return xml formatted list of node data

     */

    public String getNodeList(){

	String temp = "";

	try {

	    st = db.createStatement();



	    ResultSet rs = st.executeQuery("select name,class from nodes");



	    while(rs.next()) {

		String name = rs.getString("name");

		String n_class = rs.getString("class");

		

		temp += "<node><name>"

		    + name +

		    "</name>"

		    + "<class>"

		    + n_class

		    + "</class></node>\t";

	    }

	}

    

	catch(SQLException e) {

	    return "<error type='SQLException'>" + e.getMessage() + "</error>";

	}

	

	return "<node-list>" + temp + "</node-list>";

    }



    /** removes an edge from the database.

     * @param source source of edge to remove

     * @param dest destination of edge

     * @param e_class class of edge (in case there are multiple edges between the same two nodes)

     */

    public void removeEdge(String source, String dest, String e_class){

	System.out.println("removing edge");

	try {

	    st = db.createStatement();

	    String query = "delete from example where source='"

		+ source + "' AND dest='" + dest + "' AND class='" + e_class + "'";

	    st.executeUpdate(query);

	} catch(SQLException e) {

	    System.out.println("SQL error: " + e);

	    return;

	}

    }



    /** adds an edge to the database.

     * @param source source node of edge

     * @param dest destination node of edge

     * @param e_class class of edge

     */

    public void addEdge(String source, String dest, String e_class){

	try {

	    st = db.createStatement();

	    st.executeUpdate("insert into example (source,dest,class) VALUES ('"

					   + source + "','"

					   + dest   + "','"

					   + e_class + "')");

	} catch(SQLException e) {

	    return;

	}

    }



    /** adds a node to the database.

     * @param name label of node

     * @param n_class class of node

     */

    public void addNode (String name, String n_class) {

	try {

	    st = db.createStatement();

	    String query = "insert into nodes (name,class)"

		+ " VALUES ('" + name + "','" + n_class + "')";

	    st.executeUpdate(query);

	} catch (SQLException e) {

	    System.out.println("SQL exception: " + e);

	    return;

	}

    }



    /** removes a node from the database.

     * @param name name of node to remove.

     *

     * also removes any edges that were attached to the node.

     */

    

    public void removeNode(String name){

	try {

	    st = db.createStatement();

	    st.executeUpdate("delete from nodes where name='" +

					   name + "'");

	    st.executeUpdate("delete from example where source='" +

				 name + "'");

	    st.executeUpdate("delete from example where dest='" +

				 name + "'");

	} catch (SQLException e){

	    return;

	}

    }

    

    /** disconnects from the database.

     * @author anders

     */

    public void disconnect() {

	try {

	    if (db != null) db.close();

	}

	catch (SQLException ignored) {}

    }

}